Genetic resistance of mice to Mycobacterium paratuberculosis is influenced by Slc11a1 at the early but not at the late stage of infection

Mycobacterium avium subsp. paratuberculosis Candidate Vaccine Strains Are Pro-apoptotic in RAW 264.7 Murine Macrophages

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiological agent of Johne's disease, a severe gastroenteritis of ruminants. This study developed a model cell culture system to rapidly screen MAP mutants with vaccine potential for apoptosis. Two wild-type strains, a transposon mutant, and two deletion mutant MAP strains (MOI of 10 with 1.2 × 10⁶ CFU) were tested in murine RAW 264.7 macrophages to determine if they induce apoptosis and/or necrosis. Both deletion mutants were previously shown to be attenuated and immunogenic in primary bovine macrophages. All strains had similar growth rates, but cell morphology indicated that both deletion mutants were elongated with cell wall bulging. Cell death kinetics were followed by a real-time cellular assay to measure luminescence (apoptosis) and fluorescence (necrosis). A 6 h infection period was the appropriate time to assess apoptosis that was followed by secondary necrosis. Apoptosis was also quantified via DAPI-stained nuclear morphology and validated via flow cytometry. The combined analysis confirmed the hypothesis that candidate vaccine deletion mutants are pro-apoptotic in RAW 264.7 cells. In conclusion, the increased apoptosis seen in the deletion mutants correlates with the attenuated phenotype and immunogenicity observed in bovine macrophages, a property associated with good vaccine candidates.

Sarcoidosis, Mycobacterium paratuberculosis and Noncaseating Granulomas: Who Moved My Cheese

Clinical and histological similarities between sarcoidosis and tuberculosis have driven repeated investigations looking for a mycobacterial cause of sarcoidosis. Over 50 years ago, "anonymous mycobacteria" were suggested to have a role in the etiology of sarcoidosis. Both tuberculosis and sarcoidosis have a predilection for lung involvement, though each can be found in any area of the body. A key histopathologic feature of both sarcoidosis and tuberculosis is the granuloma-while the tuberculous caseating granuloma has an area of caseous necrosis with a cheesy consistency; the non-caseating granuloma of sarcoidosis does not have this feature. This article reviews and reiterates the complicity of the infectious agent, Mycobacterium avium subsp. paratuberculosis (MAP) as a cause of sarcoidosis. MAP is involved in a parallel story as the putative cause of Crohn's disease, another disease featuring noncaseating granulomas. MAP is a zoonotic agent infecting ruminant animals and is found in dairy products and in environmental contamination of water and air. Despite increasing evidence tying MAP to several human diseases, there is a continued resistance to embracing its pleiotropic roles. "Who Moved My Cheese" is a simple yet powerful book that explores the ways in which individuals react to change. Extending the metaphor, the "non-cheesy" granuloma of sarcoidosis actually contains the difficult-to-detect "cheese", MAP; MAP did not move, it was there all along.

Differences in susceptibility to Mycobacterium chelonae in zebrafish (Danio rerio) lines commonly used in scientific research

Mycobacteriosis is one of the most common diseases encountered in laboratory zebrafish. These infections can present a problem to researchers using zebrafish because they may introduce unknown experimental variables. Whilst differences in severity of infections between species of Mycobacterium infecting zebrafish have been well documented, little is known about differences in susceptibility between zebrafish lines. Previous surveys have found higher prevalence in the TU zebrafish line relative to other lines, suggesting that there may be underlying genetic differences in susceptibility. This study investigates Mycobacterium chelonae H1E2-GFP infections in four different zebrafish lines commonly used in research (AB, 5D, casper and TU). Fish were exposed to a labelled (green-fluorescent protein (GFP)) strain of M. chelonae by intraperitoneal injection, and infection status was evaluated after 10 weeks. Visualization of GFP in euthanized fish and histology were used as endpoints. In GFP images, severity was assessed by image analysis, and in histological sections, counts of granulomas containing acid-fast bacteria were used. Results indicated differences in severity of infections between lines, but no significant differences in prevalence.

Effect of selected single nucleotide polymorphisms in SLC11A1, ANKRA2, IFNG and PGLYRP1 genes on host susceptibility to Mycobacterium avium subspecies paratuberculosis infection in Indian cattle

Paratuberculosis (PTB) is a chronic infectious enteritis of ruminants, caused by Mycobacterium avium subspecies paratuberculosis (MAP) that brings huge economic loss to the dairy farmers. The study was conducted to explore the association of selected SNPs in IFNG, SLC11A1, ANKRA2 and PGLYRP1 genes with resistance to PTB disease in Indian cattle population. A case-control resource population was established based on the results of diagnostic tests used for detection of MAP infection status viz. ELISA, Johnin PPD test, faecal microscopy and IS900 blood PCR. The PCR-RFLP method was used for genotyping of SNPs. SNPs rs109453173 in SLC11A1, rs110853455 in IFNG and rs41933863 in ANKRA2 genes were significantly (P<0.05) associated with resistance to MAP infection. For SNP rs109453173, GG genotype and G allele was found to be associated with resistance against MAP infection than CC and CG genotypes and C allele, respectively. For SNP rs110853455, AG genotype was found to be associated with susceptibility to MAP infection than AA and GG genotype. For SNP rs41933863, the AG genotype provided three and six times more resistance against MAP infection than GG and AA genotype. The results of this study are suggestive of SNPs rs109453173, rs110853455 and rs41933863 as potential markers for screening MAP resistant cattle and a breeding programme favouring GG genotype and G allele for rs109453173, AG genotype for rs41933863 and against AG genotype for rs110853455 might confer resistance against MAP infection in Indian cattle. However, investigation of these SNPs in an independent and larger population will warrant the strength of association for resistance against MAP infection in cattle.

The Paratuberculosis Paradigm Examined: A Review of Host Genetic Resistance and Innate Immune Fitness in Mycobacterium avium subsp. Paratuberculosis Infection

Paratuberculosis, or Johne's Disease (JD) is a debilitating chronic enteritis mainly affecting ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This organism causes worldwide economic losses to the livestock industry, and is of public health importance due to the potential zoonotic risk between MAP and Crohn's disease (CD) in humans. Without economical treatments, or a vaccine capable of preventing infection without causing cross-reactions with bovine tuberculosis, test-and-cull methods for disease control are imperative. Unfortunately, difficulties in diagnostics and long subclinical stage hinder adequate control and is further complicated by variation in MAP exposure outcome. Interestingly, the majority of infections result in asymptomatic presentation and never progress to clinical disease. One contributing factor is host genetics, where polymorphisms in innate immune genes have been found to influence resistance and susceptibility to disease. Candidate genes identified across studies overlap with those found in CD and tuberculosis including; Solute carrier family 11 member 1 gene (SLC11A1), Nucleotide-binding-oligomerization domain containing gene 2 (NOD2), Major histocompatibility complex type II (MHC-II), and Toll-like receptor (TLR) genes. This review will highlight evidence supporting the vital role of these genes in MAP infection outcome, associated challenges, and implications for the future of JD research.

Survey of Candidate Single-Nucleotide Polymorphisms in SLC11A1, TLR4, NOD2, PGLYRP1, and IFNγ in Ankole Longhorn Cattle in Central Region of Uganda to Determine Their Role in Mycobacterium avium Subspecies paratuberculosis Infection Outcome

Mycobacterium avium ssp. paratuberculosis (MAP) is the cause of Johne's disease (JD) in a wide range of domestic and wild ruminants. Single-nucleotide polymorphisms (SNPs) in several genes including solute-like carrier 11A1 (SLC11A1), interferon gamma (IFNγ), Toll-like receptor 4 (TLR4), nucleotide-binding oligomerization domain 2 gene (NOD2), and bovine peptidoglycan recognition protein 1 (PGLYRP1) have been implicated in influencing the infection outcome of MAP in cattle. We have carried out a survey in a population of Ankole cattle from three districts in the central region of Uganda including Isingiro, Lyantonde, and Rakai to determine the role played by several SNPs on the above genes in the infection outcome of local cattle in Uganda. Nine hundred fifty-five heads of cattle obtained from 93 herds were tested using ELISA. Thirty-five ELISA-positive cattle and 35 negative herd mates from a total of 955 cattle tested for MAP were genotyped using iPLEX MassARRAY genotyping systems to detect the presence of a total of 13 SNPS in five different genes (SLC11A1, IFNγ, TLR4, NOD2, and PGLYRP1). The cow-level prevalence of MAP infection in Ankole Longhorn cattle in the three districts was 3.98% (35/955), while the herd-level prevalence was 27.9% and within-herd prevalence was 12 ± 1.5% (95% CI = 9.1-14.8%). The genotypes and allele frequencies of the MAP-positive cattle were compared with those of their ELISA-negative herd mates to determine the significance of the polymorphisms. The results showed that SNPs rs109915208, rs110514940, and rs110905610 on SLC11A1, c.480G>A and c.625C>A on PGLYRP1, and c.2021C>T on TLR4 were monomorphic in both seropositive and seronegative cattle and therefore had no influence on the infection outcome. The remaining SNPs studied in the five genes [SLC11A1: rs109614179; TLR4: rs29017188 (c.226G>C), c.2021C>T; NOD2: rs110536091, rs111009394; PGLYRP1: c.102G>C, c.480G>A, c.625C>A; IFNγ: rs110853455] were polymorphic, but their allele and genotype frequencies did not show any significant difference between the seropositive and seronegative cattle. No significant difference was observed for any haplotype at the gene level.

Structural characterization and molecular dynamics simulations of the caprine and bovine solute carrier family 11 A1 (SLC11A1)

Natural Resistance-Associated Macrophage Proteins are a family of transmembrane divalent metal ion transporters, with important implications in life of both bacteria and mammals. Among them, the Solute Carrier family 11 member A1 (SLC11A1) has been implicated with susceptibility to infection by Mycobacterium avium subspecies paratuberculosis (MAP), potentially causing Crohn's disease in humans and paratuberculosis (PTB) in ruminants. Our previous research had focused on sequencing the mRNA of the caprine slc11a1 gene and pinpointed polymorphisms that contribute to caprine SLC11A1's susceptibility to infection by MAP in PTB. Despite its importance, little is known on the structural/dynamic features of mammalian SLC11A1 that may influence its function under normal or pathological conditions at the protein level. In this work we studied the structural architecture of SLC11A1 in Capra hircus and Bos taurus through molecular modeling, molecular dynamics simulations in different, functionally relevant configurations, free energy calculations of protein-metal interactions and sequence conservation analysis. The results of this study propose a three dimensional structure for SLC11A1 with conserved sequence and structural features and provide hints for a potential mechanism through which divalent metal ion transport is conducted. Given the importance of SLC11A1 in susceptibility to PTB, this study provides a framework for further studies on the structure and dynamics of SLC11A1 in other organisms, to gain 3D structural insight into the macromolecular arrangements of SLC11A1 but also suggesting a potential mechanism which divalent metal ion transport is conducted.

Virulence and immunogenicity of genetically defined human and porcine isolates of M. avium subsp. hominissuis in an experimental mouse infection

Mycobacterium avium subsp. hominissuis (Mah) represents a health concern for humans and to a lesser extent for pigs, but its zoonotic potential remains elusive. Using multispacer sequence typing (MST) we previously identified 49 different genotypes of Mah among Belgian clinical and porcine isolates, with 5 MSTs shared by both hosts. Using experimental intranasal infection of BALB/c mice, we compared the virulence and immunogenicity of porcine and clinical human isolates with shared genotype or with a genotype only found in humans or pigs. Bacterial replication was monitored for 20 weeks in lungs, spleen and liver and mycobacteria specific spleen cell IFN-γ, IL-10 and IL-17 production as well as serum antibody responses were analyzed. Isolates varied in virulence, with human and porcine isolates sharing MST22 genotype showing a thousand fold higher bacterial replication in lungs and more dissemination to spleen and liver than the human and porcine MST91 isolates. Virulent MST22 type was also associated with progressive suppression of IFN-γ and IL-17 responses, and increased IL-10 production. Whole genome sequencing of the two virulent isolates with MST22 genotype and two avirulent isolates of genotype MST91 and comparison with two well-studied M. avium subsp. hominissuis reference strains i.e. Mah 104 and Mah TH135, identified in the two MST22 isolates nine specific virulence factors of the mammalian cell entry family, that were identical with Mah 104 strain. Despite the obvious limitations of the mouse model, a striking link of virulence and identity at the genome level of porcine and human isolates with the same multisequence type, for which no correlation of place of residence (humans) or farm of origin (pigs) was observed, seems to point to the existence in the environment of certain genotypes of Mah which may be more infectious both for humans and pigs than other genotypes.

Host Transcriptional Profiles and Immunopathologic Response following Mycobacterium avium subsp. paratuberculosis Infection in Mice

Paratuberculosis or Johne’s disease is a chronic granulomatous enteropathy in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection. In the present study, we examined the host response to MAP infection in spleens of mice in order to investigate the host immunopathology accompanying host-pathogen interaction. Transcriptional profiles of the MAP-infected mice at 3 and 6 weeks p.i. showed severe histopathological changes, whereas those at 12 weeks p.i. displayed reduced lesion severity in the spleen and liver. MAP-infected mice at 3 and 6 weeks p.i. showed up-regulation of interferon-related genes, scavenger receptor, and complement components, suggesting an initial innate immune reaction, such as macrophage activation, bactericidal activity, and macrophage invasion of MAP. Concurrently, MAP-infected mice at 3 and 6 weeks p.i. were also suggested to express M2 macrophage phenotype with up-regulation of Mrc1, and Marco and down-regulation of MHC class II, Ccr7, and Irf5, and canonical pathways related to the T cell response including ICOS-ICOSL signaling in T helper cells, calcium-induced T lymphocyte apoptosis, and CD28 signaling in T helper cell. These results provide information which furthers the understanding of the immunopathologic response to MAP infection in mice, thereby providing insights valuable for research into the pathogenesis for MAP infection.

Functional analysis of 3'UTR polymorphisms in the caprine SLC11A1 gene and its association with the Mycobacterium avium subsp. paratuberculosis infection

The study aimed to investigate whether the genetic polymorphisms in the 3'UTR of the caprine SLC11A1 gene are functional, and to assess the role of MAP as a regulatory parameter in gene expression. To this goal we constructed plasmids expressing the Luciferase reporter gene in transient transfections of a mouse (Balb/c) macrophage cell line (RAW264.7), incorporating those polymorphisms that our previous work indicated as more prominent in terms of SLC11A1 expression and responsiveness to MAP infection. Gene expression variation was recorded on the average of the respective measurements after exposure to Mycobacterium avium subsp. paratuberculosis (MAP) combined with microbial antigens and cytokines. In silico analysis of the region under study allowed identification of one cis-acting RNA element, five putative transcriptional regulatory elements and 85 3'end microRNA binding sites. The two polymorphic regions (regions A and B) of the 3'UTR of the caprine SLC11A1 gene were recognized as regulators of its activity, at transcriptional and post-transcriptional level. The GT16 polymorphism at region A, combined with the GT8 polymorphism at region B, results in up-regulation of the SLC11A1 gene. The specific genotype was also found to be more responsive to MAP exposure at a statistically significant level.

Mycobacterium avium ss. paratuberculosis Zoonosis - The Hundred Year War - Beyond Crohn's Disease

The factitive role of Mycobacterium avium ss. paratuberculosis (MAP) in Crohn's disease has been debated for more than a century. The controversy is due to the fact that Crohn's disease is so similar to a disease of MAP-infected ruminant animals, Johne's disease; and, though MAP can be readily detected in the infected ruminants, it is much more difficult to detect in humans. Molecular techniques that can detect MAP in pathologic Crohn's specimens as well as dedicated specialty labs successful in culturing MAP from Crohn's patients have provided strong argument for MAP's role in Crohn's disease. Perhaps more incriminating for MAP as a zoonotic agent is the increasing number of diseases with which MAP has been related: Blau syndrome, type 1 diabetes, Hashimoto thyroiditis, and multiple sclerosis. In this article, we debate about genetic susceptibility to mycobacterial infection and human exposure to MAP; moreover, it suggests that molecular mimicry between protein epitopes of MAP and human proteins is a likely bridge between infection and these autoimmune disorders.

Virulence and immunity orchestrated by the global gene regulator sigL in Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis causes Johne's disease in ruminants, a chronic enteric disease responsible for severe economic losses in the dairy industry. Global gene regulators, including sigma factors are important in regulating mycobacterial virulence. However, the biological significance of such regulators in M. avium subsp. paratuberculosis rremains elusive. To better decipher the role of sigma factors in M. avium subsp. paratuberculosis pathogenesis, we targeted a key sigma factor gene, sigL, activated in mycobacterium-infected macrophages. We interrogated an M. avium subsp. paratuberculosis ΔsigL mutant against a selected list of stressors that mimic the host microenvironments. Our data showed that sigL was important in maintaining bacterial survival under such stress conditions. Survival levels further reflected the inability of the ΔsigL mutant to persist inside the macrophage microenvironments. Additionally, mouse infection studies suggested a substantial role for sigL in M. avium subsp. paratuberculosis virulence, as indicated by the significant attenuation of the ΔsigL-deficient mutant compared to the parental strain. More importantly, when the sigL mutant was tested for its vaccine potential, protective immunity was generated in a vaccine/challenge model of murine paratuberculosis. Overall, our study highlights critical role of sigL in the pathogenesis and immunity of M. avium subsp. paratuberculosis infection, a potential role that could be shared by similar proteins in other intracellular pathogens.

Impact of host genetics on susceptibility and resistance to Mycobacterium avium subspecies Paratuberculosis infection in domestic ruminants

Johne's disease or Paratuberculosis has emerged as major infectious disease of animals in general and domestic livestock in particular on global basis. There have been major initiatives in developed countries for the control of this incurable malady of animals and human beings alike (inflammatory bowel disease or Crohn's disease). Disease has not received similar attention due to inherent complexities of disease, diagnosis and control, in resource poor counties around the world. However, the rich genetic diverstiy of the otherwise low productive animal population offers opportunity for the control of Johne's disease and improve per animal productivity. Present review aims to gather and compile information available on genetics or resistance to Johne's disease and its future exploitation by resource poor countries rich in animal diversity. This review will also help to create awareness and share knowledge and experience on prevalence and opportunities for control of Johne's disease in the livestock population to boost per animal productivity among developing and poor countries of the world. Breeding of animals for disease resistance provides good, safe, effective and cheaper way of controlling Johne's disease in animals, with especial reference to domestic livestock of developing and poor countries. Study will help to establish better understanding of the correlation between host cell factors and resistance to MAP infection which may have ultimately help in the control of Johne's disease in future.

Host responses to persistent Mycobacterium avium subspecies paratuberculosis infection in surgically isolated bovine ileal segments

A lack of appropriate disease models has limited our understanding of the pathogenesis of persistent enteric infections with Mycobacterium avium subsp. paratuberculosis. A model was developed for the controlled delivery of a defined dose of M. avium subsp. paratuberculosis to surgically isolated ileal segments in newborn calves. The stable intestinal segments enabled the characterization of host responses to persistent M. avium subsp. paratuberculosis infections after a 9-month period, including an analysis of local mucosal immune responses relative to an adjacent uninfected intestinal compartment. M. avium subsp. paratuberculosis remained localized at the initial site of intestinal infection and was not detected by PCR in the mesenteric lymph node. M. avium subsp. paratuberculosis-specific T cell proliferative responses included both CD4 and γδ T cell receptor (γδTcR) T cell responses in the draining mesenteric lymph node. The levels of CD8(+) and γδTcR(+) T cells increased significantly (P < 0.05) in the lamina propria, and M. avium subsp. paratuberculosis-specific tumor necrosis factor alpha (TNF-α) and gamma interferon secretion by lamina propria leukocytes was also significantly (P < 0.05) increased. There was a significant (P < 0.05) accumulation of macrophages and dendritic cells (DCs) in the lamina propria, but the expression of mucosal toll-like receptors 1 through 10 was not significantly changed by M. avium subsp. paratuberculosis infection. In conclusion, surgically isolated ileal segments provided a model system for the establishment of a persistent and localized enteric M. avium subsp. paratuberculosis infection in cattle and facilitated the analysis of M. avium subsp. paratuberculosis-specific changes in mucosal leukocyte phenotype and function. The accumulation of DC subpopulations in the lamina propria suggests that further investigation of mucosal DCs may provide insight into host responses to M. avium subsp. paratuberculosis infection and improve vaccine strategies to prevent M. avium subsp. paratuberculosis infection.

M. paratuberculosis Heat Shock Protein 65 and Human Diseases: Bridging Infection and Autoimmunity

Mycobacterium avium subspecies paratuberculosis (MAP) is the known infectious cause of Johne's disease, an enteric inflammatory disease mostly studied in ruminant animals. MAP has also been implicated in the very similar Crohn's disease of humans as well as sarcoidosis. Recently, MAP has been associated with juvenile sarcoidosis (Blau syndrome), autoimmune diabetes, autoimmune thyroiditis, and multiple sclerosis. While it is intuitive to implicate MAP in granulomatous diseases where the microbe participates in the granuloma, it is more difficult to assign a role for MAP in diseases where autoantibodies are a primary feature. MAP may trigger autoimmune antibodies via its heat shock proteins. Mycobacterial heat shock protein 65 (HSP65) is an immunodominant protein that shares sequential and conformational elements with several human host proteins. This molecular mimicry is the proposed etiopathology by which MAP stimulates autoantibodies associated with autoimmune (type 1) diabetes, autoimmune (Hashimoto's) thyroiditis, and multiple sclerosis. This paper proposes that MAP is a source of mycobacterial HSP65 and acts as a trigger of autoimmune disease.

Mechanisms of resistance and susceptibility to experimental visceral leishmaniosis: BALB/c mouse versus Syrian hamster model

Several animal models have been established to study visceral leishmaniosis (VL), a worldwide vector-borne disease affecting humans and domestic animals that constitutes a serious public health problem. BALB/c mice and Syrian hamsters are the most widely used experimental models. In this paper, we summarize the advantages and disadvantages of these two experimental models and discuss the results obtained using these models in different studies of VL. Studies using the BALB/c mouse model have underscored differences between the liver and spleen in the course of VL, indicating that pathological evaluation of the visceral organs is essential for understanding the immune mechanisms induced by Leishmania infantum infection. The main goal of this review is to collate the relevant literature on Leishmania pathogenesis into a sequence of events, providing a schematic view of the main components of adaptive and innate immunity in the liver and spleen after experimental infection with L. infantum or L. donovani. This review also presents several viewpoints and reflections about some controversial aspects of Leishmania research, including the choice of experimental model, route of administration, inoculum size and the relevance of pathology (intimately linked to parasite persistence): a thorough understanding of which is essential for future VL research and the successful development of efficient control strategies for Leishmania spp.

Candidate gene and genome-wide association studies of Mycobacterium avium subsp. paratuberculosis infection in cattle and sheep: a review

Paratuberculosis (Johne's disease), caused by Mycobacterium avium subspecies paratuberculosis, is responsible for significant economic losses in livestock industries worldwide. This organism is also of public health concern due to an unconfirmed link to Crohn's disease. Susceptibility to paratuberculosis has been suggested to have a genetic component. In livestock, a number of candidate genes have been studied, selected on their association to susceptibility in other mycobacterial diseases, their known role in disease pathogenesis or links to susceptibility of humans to Crohn's disease. These genes include solute carrier family 11 member 1 (SLC11A1, formerly NRAMP1), toll-like receptors, caspase associated recruitment domain 15 (CARD15, formerly NOD2), major histocompatibility complex (MHC) and cytokines (interleukin-10 and interferon-gamma) and their receptors. Genome wide association studies have attempted to confirm associations found and identify new genes involved in pathogenesis and susceptibility. There are a number of limitations and difficulties in these approaches, some peculiar to paratuberculosis but others generally applicable to identification of genetic associations for complex traits. The technical approaches and available information for paratuberculosis have expanded rapidly, particularly relating to sheep and cattle. Here we review the current published evidence for a genetic association with paratuberculosis susceptibility, technological advances that have progressed the field and potential avenues for future research.

Identification of single nucleotide polymorphisms in the bovine solute carrier family 11 member 1 (SLC11A1) gene and their association with infection by Mycobacterium avium subspecies paratuberculosis

Johne's disease is a chronic enteritis caused by Mycobacterium avium ssp. paratuberculosis (MAP) that causes substantial financial losses for the cattle industry. Susceptibility to MAP infection is reported to be determined in part by genetic factors, so marker-assisted selection could help to obtain bovine populations that are increasingly resistant to MAP infection. Solute carrier family 11 member 1 (SLC11A1) was adjudged to be a potential candidate gene because of its role in innate immunity, its involvement in susceptibility to numerous intracellular infections, and its previous association with bovine MAP infection. The objectives of this study were to carry out an exhaustive process of discovery and compilation of polymorphisms in SLC11A1 gene, and to perform a population-based genetic association study to test its implication in susceptibility to MAP infection in cattle. In all, 57 single nucleotide polymorphisms (SNP) were detected, 25 of which are newly described in Bos taurus. Twenty-four SNP and two 3'-untranslated region polymorphisms, previously analyzed, were selected for a subsequent association study in 558 European Holstein-Friesian animals. The SNP c.1067C>G and c.1157-91A>T and a haplotype formed by these 2 SNP yielded significant association with susceptibility to MAP infection. The c.1067C>G is a nonsynonymous SNP that causes an amino acid change in codon 356 from proline to alanine (P356A) that could alter SLC11A1 protein function. This association study supports the involvement of SLC11A1 gene in susceptibility to MAP infection in cattle. Our results suggest that SNP c.1067C>G may be a potential causal variant, although functional studies are needed to assure this point.

Vaccination against paratuberculosis

Johne's disease, or paratuberculosis, is a chronic granulomatous enteritis in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) affecting principally cattle, sheep and goats. Primarily, there are two clinical signs: cachexia and chronic diarrhea (less common in goats and sheep). This disease results in considerable economic losses in livestock industry, particularly the dairy sector. The route of transmission is mostly by the fecal-oral route, but hygienic measures and culling of shedding animals are not sufficient to eradicate this disease. Moreover, diagnostic tools available at this moment are not powerful enough to perform early and specific diagnosis. Existing vaccines, based on whole killed or live-attenuated bacteria, can delay the onset of clinical symptoms but do not protect against infection. Moreover, vaccinated animals develop antibodies that interfere with existing serodiagnostic tests for paratuberculosis and they become reactive in the tuberculin skin test, used for the control of bovine tuberculosis. This review summarizes the current knowledge of the immune responses induced by MAP infection, with focus on cattle studies. It provides an overview of the existing MAP vaccines and comments on the development of second-generation subunit vaccines based on new technologies.